Producing oxidized carbon



- Patented Aug. 23, 1927.

STATES 'onvnn w. s'ron'a'x AND eoanon r. connmson, or

PATENT OFFICE.

Manson, Wisconsin, 'nssronons IO 0. F. BURGESS LABORATORIES, INC., OFDOVER, DELAWARE, A O OBPORA'1ION OF DELAWARE.

2H0 matting.

, This invention relates to the electrochemical production of solidcarbon oxide or oxides having the properties of graphitic oxide. I

In a copending application of Bruce K. Brown, Serial No. 42,091, filedJuly 7, 1925', a method'for the electrochemical production of carbonoxides is disclosed; This method consists in mounting carbonaceousmaterial as anode in an oxidizing electrolyte, such as 30% nitric acidatabout roonitempera ture, and passing an electric current having adensity of about ten amperes per square foot of anode surface. The anodedisintegrates toa sludge which is a mixture of carbon and oxide ofcarbon and may 'contain as high as 6% by weight of available oxygen.Carbon so-oxidized does not have the yellow color of pure graphiticoxide but has the dull black appearance of partially oxidized carbonand'it apparently is-iden tical or approximately identical with theproduct obtained b chemical oxidation. We

ave found that t e yield and oxygen percentage of the oxidized carbonproduct may be greatly increasedby suitably treating the electrodes thatare to be disintegrated and further by the maintainin of the cell at theproper temperature w liile using elec- Q trodes so treated.

If a graphitic or other carbonaceous electrode is used as an anode in adilute nitric acid or other suitable electrolite for the production ofoxidized carbon t e electrode disintegrates at a rate depen upon thecomposition of the electro yte current density, temperature of theelectro yte and composition of the electrode. Usuall an untreated anodewhich is disintegrate -in dilute 40 nitric acid at room tem eraturedisintegrates into a product that vanes over a wide range of particlesizes. The coarser articles may be as large as walnuts while the finerpar ticles maypass through a 100 mesh screen.

5 All of these particles have a coating of oxidized carbon. on a weightbasis the coarser particles have a relatively percenta en whereas thesmall particles will have a igh percentage if the coating. is of thesame of the electrode.

It is "readily sun that raonucme oxrnrzan cannon.

Application filed my 7, 1935; Serial No. 42,111.

thickness on all particles. This is borne out I in Opractice, since thefinely disintegrated p uct is found to have the higher percentage ofavailable 0 gen. As an. illustration, if thatpart 0 the product from anuntreated graphite anode which will pass through 100 mesh has anavailable oxygen percentage of about 5 percent, that part of the productwhich-passes through 40 mesh butis retained on 100 mesh will have anavailable oxygen percentage of about 4: per-' cent. Similarly thepercentage of oxygen gradually decreases as the particles increase '11size, until the coarsest particles contain considerably less than 1 percent of oxygen. While it'is possible to utilize such a productindustrially by screening out the coarser lumps, the coarse lumpsrepresent a considerable loss, as they 0 en constitute 25 per cent ormore of the entire product. We have found that thephysical'disintegration of the anodes results from the penetration ofthe electrolyte The ordina molded electrode is porous to a considera 1edegree and into the pores in the case of graphite even the'i'ndividua-l1 particles are porous to the'extent that they are laminated. As theelectrolyte penetrates into the pores of the electrode, the currentfinds a path into the interior oi the electrodef, The electrolysis ofthe oxidizing electrolyte in the pores of the carbonaceous mate- -ri 1results in the oxidation of the carbon to a solid oxide of carbon. Theformation of the solid oxide is accompanied by a rceptible increase involume or swel g. This causes physical disintegration; We have foundthat his may he ate ped. The remedy is to prevent the electro yte fromentering the ores of the electrode.

I e easiest method of preventing the e'lectrolyte from entering thepores of the electrode is to fill: these with a; water ,Paralfiningi theout and it is' very he formation of can be made repellent, suchv as parelectrpde is easily camel effective in reventing large lumps in fact, aproduct all of WhlC screen and per cent'of through a 60 mesh screen.

chwillpass will pass through a 20 meshfined. 'The melted para Not onlydoes the parafiin prevent the disintegration of the electrode into largelumps but it also raises the percenta e of fixed oxygen. If an untreatedgraphlte electrode is disintegrated in a dilute nitric acid electrolyte,the fixed oxygen in the product passing throu h a 60 mesh screen will beapproximate y five percent. By paraflining the anode, the disintegrationproduct passing through 60 mesh will contain between 9 and 10 percent ofoxygen. The increase in the fixed oxygen content obtained when anelectrode is saturated with paraflin can probably be explained on thetheory that theelectrolyte is prevented from penetrating the pores ofthe carbon, and instead, allows the electrolyte to penetrate theparticles of carbon-and thereby rupture these. In the case of graphite,the electrolyte no doubt penetrates between the laminations, whereasthis robably does not occur when the graphite 1s unparafiined. The'paraflining results-in a much better penetration of the individualparticles in contrast to the penetration of the electrolyte into thespaces around the'separate particles when unparafcarried out b'immersing it in smoking-hot fliii for a time long enough toefi'ectc'omplete enetration.

While para ing of the electrode is a cheap and efiicient' method forsecuring a disintegration into fine particles by confining thisdisintegration and oxidation to the surface of the electrode in contactwith the electrolyte, it is possible to use a Wide va- 'riety of slmilarwax-like and other water repellant materials such as rosin. It is alsoossible to use ordinary lubricating oils. iscarded crank case oil is acheap and eflicient oil. which may be used to displace themore expensiverefined. oils. The electrodes may-even be saturated with asoline,naptha, carbon tetrachloride and similar s01- vents, preferably thosenot easily attacked liiy the oxidizing reactions at the anode, helrefl'ect, however, is not as permanent,

since they are gradually driven out during v the electrolysis, sothatthe product contains particles of increasing size asthe'electrolysis proceeds.

' It 1s notnecessary to use oils, waxes, or

' solvents of a water re llant nature, as an material will work w 1chwill'prevent di fusion of the electrolyte and confine the oxidation anddisintegration to the surface of the electrode in contact with theelectrolyte. An electrode thoroughly soaked in water will show thecharacteristics oi a parafiined anode for a time until the electrolytehas so diffused into .the interior that the li uid in thepores becomesconductive enoug to conduct the current sufiiciently to causeelectrochemical oxidation. The electrode may be saturated with watersolutions of paraflining of an anode may be' various chemical reagentswhich will cut down the rate of electrolyte diffusion.

It is also possible to saturate the electrode with a solution of areagent such as sodium silicate which will form an insoluble precipitateor gel when it comes in contact with the electrolyte and will therebyprevent diffusion into the interior of the electrode. The precipitateshould be of such a nature that it maybe subsequently washed out of theoxidized carbon, or if it is not washed out, should be harmless for theuses to which the oxidized carbon is put.

After the disintegration of the electrode, the powdered material iswashed with water to remove the electrolyte or other chemicals that maybe present If a moisture repellant is used to saturate. the electrode,this material is found in the disintegration product. This may beremoved by suitable solvents, especiallysuch solvents as boil below 100C. If the oxide of carbon has to be heated much above 100 C. there is anappreciable deterioration of the oxide. Carbon tetrachloride is aneflicient extracting agent when paraflin is used for saturating theelectrode. It has the distinct advantage of not being flammable but hasthe disadvantage of high cost. Benzole is also an efiective agent, whileordinary gasoline has high boiling fractions present which cannot bedriven readily from the colloidal oxide of carbon. The moisturerepellant may be extracted in the cold but is more easily removed byboilin under a reflux condenser 100 and washing wit pure solvent, thoughthis procedure tends to drive as some of the Y oxygen also. The solventand the moisture repellant may be recovered by distillation.

If carbon tetrachloride or similar volatile solvents are used forsaturating the electrodes during electrolysis it does not becomenecessary to extract these from the oxide of carbon. Simply heating theoxide to above the boilin point of the solvent drives off the solvent.Ihe advantages of this procedure are apparent.

If the oxide of carbon is used for depolarizing purposes in electricbatteries it is essential that practically all of the moisture 1repellant be extracted. Even small amounts .of parafiin will greatlydecrease the conducresults are obtained below 0- G. At this lowtemperature the benzole freezes and acts as a solid moisture repellent.At ordinary temperatures the benzole is apparently ox'- idized morerapidly than the carbon and in some of our experiments has decreased theyield of oxidized carbon. These results indicate that it is. preferableto have a saturating medium which will be less readily. oxidized thanthe carbon, or the tem erature should be so regulated that this conition is realized, as in the case of the benzole.

Throughout the specification and claims carbon is used in the broadersense and includes the graphitic state of the element.

Carbonaceous material .is used throughout rial containing free carboninany of its allo-' the specification and claims to cover a matetropicforms.

We claim: 1, The method of producing pulverous, oxidized carbonconsisting essentiall of-submitting an anode of-carbon which as beentreated to confine the oxidation and disintegration of the electrode tothe surface in contact with the electrolyte to an electric current in abath having an oxidizing oxygen containin anion.

2. The met 0d of producin' *pulverous, oxidized carbon all of whic willpass through a 20 mesh screen consisting essentially of submittingananode of carbon which has been treated to confine the oxidation anddisintegration of the electrode to the surface in contact with theelectrolyte to an electric current in a bath having an oxidizing-oxygencontaining anion. a

3. The method of producing pulverous, oxidized carbon consistlngessentially of submitting an anode of carbon that has been impregnatedwith a moisture repellent to an electric current in a bath having anoxidizing oxygen containing anion.

4. The method of producin pulverous, oxidized carbon all of whic willpass through a 20 mesh screen consisting essentially of submitting anyanode of carbon that has been impregnated with agmoisture repellent toan electric current in a bath having an oxldizing oxygen containinganion.

V peratures bonaceous material of such anode to an electric current in abath having an oxidizing oxygen containing anion.

7. The method of producing oxidized carbon-in pulverous form consistingessentially of submitting an anode of carbonaceous material that hasbeen impregnated with parafiin to an electric current in a bath havingan oxidizing oxygen containing anion.

8. The method of producing pulverous, oxidized carbon consistingessentially of submitting an anode of carbon that has been impregnatedwith a moisture repellant to an electric current in a bath having anoxydizing oxygen containing anion and leaching with water the product soformed.

9. The -method of producing pulverous, oxidized carbon consistingessentially of submitting an anode of carbon that has been im-- productso, formed with water and with a solvent capable of extracting themoisture repellant. v

10. The method of producing pulverous, oxidized carbon consistingessentiallv of submitting an anode of carbon that has been impregnatedwith a moisture repellant to an electric current in a bath having anoxidizing oxy en containing anion and leaching the product so formedwith water and benzol.

11. The method of producing pulverous, oxidized carbon consistingessentially of submitting an anode of carbonaceous material that hasbeen impregnated with a moisture repellent to an electric current in abath containing nitric acid.

12. The method of producing pulverous. oxidized carbon consistingessentially of submitting an anode of carbonaceous material that hasbeen impregnated with a moisture repellant to an electric current in abath containin nitric acid and sodium dichromate.

13. The method of producing oxidized carbon consisting essentially ofsubmitting an anode of carbonaceous material that has been impregnatedwith paraffin to an electric current in a bath having an oxidizingoxygen containing anion and leaching the product so formed with waterand benzol.

.145. The method of produ g oxidized carbon consisting essentially ofsubmitting an anode of carbonaceous m terial impregnated with a moisturerepellant to an electric current in a bath having an oxidizing oxygengontiaining anion at a temperature. below .15. The method of producingoxidized carbon consisting essentially of submitting an "anode ofcarbonaceous material impregnated with a'moisture repellant to anelectric current 1n a bath having.- an oxidizing oxygen ous form capableof passing through a 20 mesh screen and containing a moisturerepella-nt. 10

In testimony whereof we aflix our signatures.

OLIVER W. STOREY. GORDON T. GOLLINSON.

